The present invention relates to a cleaning unit employed in electrophotographic copiers, printers, and the like, an image forming method and an image forming apparatus employing said cleaning unit.
In recent years, organic photoreceptors (hereinafter referred simply to as photoreceptors), comprising organic photoconductive materials, have been the most widely employed image bearing bodies in electrophotographic image forming apparatuses. Compared to other photoreceptors, organic photoreceptors exhibit advantages in such a manner that it is easy to develop materials which correspond to various types of exposure light sources ranging from visible light to infrared rays; it is possible to select materials which result in minimum environmental pollution; their production cost is lower, and the like. However, said organic photoreceptors do exhibit one disadvantage in that the mechanical strength is insufficient, and during production of numerous copies and prints, the photoreceptor surface tends to be degraded or abraded.
Further, said organic photoconductor exhibits large contact energy with the toner, which visualizes the electrostatic latent images formed on the photoreceptor. As a result, it is difficult to remove the resulting residual toner, which remains on the photoreceptor after transferring said toner image onto a transfer material in the transfer process. Thus various problems regarding the cleaning on the photoreceptor surface tend to occur.
On the other hand, due to the progress of digital technology in recent years, an image forming method utilizing a digital system has played an increasing role in the image forming method utilizing the electrophotographic system. The image forming method utilizing said digital system is basically carried out in such a manner that an image, comprised of small dots called pixels, of 400 dpi, and the like, can be visualized. Demanded thus is a high image quality technique which faithfully reproduces images comprised of such small dots.
In order to realize such desired high image quality technique, one of the most important techniques is that which relates to toner production. Heretofore, for forming electrophotographic images, mainly employed have been so-called pulverized toners which are prepared in such a manner that toner powder, which is obtained by blending and kneading binder resins with pigments and then pulverizing the resultant mixture, is subjected to classification during a classifying process. However, the toner obtained through such production processes is limited in uniform particle size distribution of toner particles. As a result, the particle size distribution, as well as the shape of toner particles, has not been sufficiently uniform. Thus in electrophotographic images obtained by employing such pulverized toner, it is difficult to achieve the desired high image quality.
In recent years, as a means to achieve uniform size distribution as well as uniform shape of said toner particles, proposed have been electrophotographic developer materials or image forming methods utilizing polymerized toner. Said polymerized toner is produced by uniformly dispersing monomers as the raw material in a water based system and then polymerizing the resultant dispersion. As a result, it is possible to obtain a toner having a uniform size distribution as well as uniform shape.
Herein, when said polymerized toner is applied to an image forming apparatus utilizing an organic photoconductor, new technical problems have surfaced. Namely, as described above, the toner particle shape of said polymerized toner is formed during the monomer polymerization process. As a result, formed is a nearly spherical shape. As is already well known, toner of a spherical shape, which remains on said organic photoreceptor, tends to be insufficiently removed. Specifically, the surface of the organic photoreceptor tends to be worn. When toner particles adhere to the roughened surface, caused by said wear, fine toner particles are not completely removed by cleaning, in such a range that the resultant images are not visually affected. Such toner particles, which have not been removed, stain charging members (such as charging wires and charging rollers). As a result, halftone images, and the like, result in image unevenness.
In order to improve the insufficient cleaning which results in the image forming method, utilizing polymerized toner as described above, heretofore, various proposals have been made. of these, applied has been one proposal in which the shape of the polymerized toner is varied from a circular shape to an elliptic one, and another in which the surface shape of the polymerization toner surface is varied into an irregular one. However, these proposals have not sufficiently overcome the stated problems.
An objective of the present invention is to provide a cleaning unit which overcomes the aforementioned problems, and upon using an organic photoreceptor and a polymerized toner, maintains the desired cleaning performance for an extended period of time, results in no image problems and is capable of forming excellent electrophotographic images, and an image forming method, as well as an image forming apparatus using said cleaning unit.
In order to overcome the aforementioned problems, the inventors of the present invention conducted persistent investigations. As a result, it became possible to secure excellent cleaning properties as well as to maintain stable vibration of the cleaning blade by adjusting torque variation generated between the photoreceptor and the cleaning blade into an optimal range. Thus, it became possible to overcome said problems. Namely, it was discovered that the objective of the present invention was achieved by utilizing any of constitutions described below.
A cleaning unit having a cleaning blade which removes residual toner from an organic photoreceptor after development of an electrostatic latent image formed on said organic photoreceptor, employing a developer comprising a toner and subsequently transferring a toner image, visualized through said development, onto a transfer material from said organic photoreceptor, a cleaning unit wherein said cleaning unit is constituted so as to satisfy the aforementioned relational expression, Formula 2, when the variation of dynamic torque values of from 10 Hz to 10 kHz, generated between said organic photoreceptor and said cleaning blade, is expressed by the aforementioned Formula 1.
T=xcexa3{(X2n-1)2+(X2n)2}, n=1 to 12 xe2x80x83xe2x80x83Formula 1 
M={xcexa3(X2n-1+X2n))2/24, n=1 to 12
N={(xcexa3X2n-1)2+(xcexa3X2n)2}/12 - M, n=1 to 12 
E=(T - M -N)/22 
wherein
X2n-1: Maximum value of dynamic torque from (n-1) to n minute in N-m, wherein n is 1 to 12.
X2n: Minimum value of dynamic torque from (n-1) to n minute in N-m.
Sxe2x89xa713xe2x80x83xe2x80x83Formula 2 
wherein
S=10log{(M - E)/24E}
A cleaning unit having a cleaning blade which removes residual toner from an organic photoreceptor after development of an electrostatic latent image formed on said organic photoreceptor, employing a developer comprising a toner and subsequently transferring a toner image, visualized through said development, onto a transfer material from said organic photoreceptor, a cleaning unit wherein said cleaning unit is constituted so as to satisfy the aforementioned relational expression, Formula 3, when the variation of dynamic torque values of from 10 Hz to 10 kHz, generated between said organic photoreceptor and said cleaning blade, is expressed by the aforementioned Formula 1.
0.00 less than K less than 0.9xe2x80x83xe2x80x83Formula 3
wherein
K={square root over ( )}{(M - E)/24}
A cleaning unit having a cleaning blade which removes residual toner from an organic photoreceptor after developing an electrostatic latent image formed on said organic photoreceptor, employing a developer comprising a toner and subsequently transferring a toner image, visualized through said development, onto a transfer material from said organic photoreceptor, a cleaning unit wherein said cleaning unit is constituted so as to satisfy the aforementioned relational expression, Formula 4, when the variation of dynamic torque values of from 10 Hz to 10 kHz, generated between said organic photoreceptor and said cleaning blade, is expressed by the aforementioned Formula 1.
0 less than Gxe2x89xa60.1xe2x80x83xe2x80x83Formula 4 
wherein
G={square root over (E)}
A cleaning unit having a cleaning blade which removes residual toner from an organic photoreceptor after development of an electrostatic latent image formed on said organic photoreceptor, employing a developer comprising a toner and subsequently transferring a toner image, visualized through said development, onto a transfer material from said organic photoreceptor, a cleaning unit wherein said cleaning unit is constituted so as to satisfy the aforementioned relational expression, Formula 5, when the variation of dynamic torque values of from 10 Hz to 10 kHz, generated between said organic photoreceptor and said cleaning blade, is expressed by the aforementioned Formula 1.
0 less than H less than 0.2 xe2x80x83xe2x80x83Formula 5
wherein
H=xcexa3(X2n-1)/12-xcexa3(X2n)/12, n=1 to 12
A cleaning unit having a cleaning blade which removes residual toner from an organic photoreceptor after development of an electrostatic latent image formed on said organic photoreceptor, employing a developer comprising a toner and subsequently transferring a toner image, visualized through said development, onto a transfer material from said organic photoreceptor, a cleaning unit wherein said cleaning unit is constituted so as to satisfy the aforementioned relational expression, Formula 6, when the variation of dynamic torque values of from 10 Hz to 10 kHz, generated between said organic photoreceptor and said cleaning blade, is expressed by the aforementioned Formula 1.
0.1 less than Jxe2x89xa60.8xe2x80x83xe2x80x83Formula 6
wherein
J=xcexa3{ (X2n-1)+(X2n) }/24, n=1 to 12
A cleaning unit having a cleaning blade which removes residual toner from an organic photoreceptor after development of an electrostatic latent image formed on said organic photoreceptor, employing a developer comprising a toner and subsequently transferring a toner image, visualized through said development, onto a transfer material from said organic photoreceptor, a cleaning unit wherein said cleaning unit is constituted so as to satisfy the aforementioned relational expression, Formulas 2 through 6, when the variation of dynamic torque values of from 10 Hz to 10 kHz, generated between said organic photoreceptor and said cleaning blade, is expressed by the aforementioned Formula 1.
The above cleaning units can employ toner which has a variation coefficient of the shape coefficient of said toner particles of no more than 16 percent as well as has a number variation coefficient of the number size distribution of said toner particles of no more than 27 percent.
The above cleaning units can employ toner which comprises at least 65 percent by number of toner particles having a shape coefficient in the range of from 1.2 to 1.6.
The above cleaning units can employ toner which comprises at least 50 percent by number of toner particles having no corners.